.. _innodb_buffer_pool_shm:
===========================
Shared Memory Buffer Pool
===========================
The :ref:`SHM buffer pool ` patch, which provided the ability to use a shared memory segment for the buffer pool to enable faster server restarts, has been removed. Instead, we recommend using the :ref:`LRU Dump/Restore ` patch which provides similar improvements in restart performance.
Replacement is due to ``SHM`` buffer pool both being very invasive and not widely used. Improved restart times are better provided by the much safer ``LRU D/R`` patch which has the advantage of also persisting across machine restarts.
The configuration variables for :file:`my.cnf` have been kept for compatibility and warnings will be printed for the deprecated options (:variable:`innodb_buffer_pool_shm_key` and :variable:`innodb_buffer_pool_shm_checksum`) if used.
Instructions for disabling the ``SHM`` buffer pool can be found :ref:`here `.
Instructions on setting up ``LRU`` dump/restore can be found :ref:`here `.
Version Specific Information
============================
* :rn:`5.1.49-rel12.0`
Feature introduced.
* :rn:`5.1.50-rel12.1`
System variable :variable:`innodb_buffer_pool_shm_checksum` added.
* :rn:`5.1.58-12.9`
Feature removed, as LRU Dump/Restore is less invasive, more
reliable and a better solution.
System Variables
================
.. variable:: innodb_buffer_pool_shm_key
:cli: Yes
:conf: Yes
:scope: Global
:dyn: No
:vartype: Boolean
:default: OFF
:range: ON/OFF
.. variable:: innodb_buffer_pool_shm_checksum
:cli: Yes
:conf: Yes
:scope: Global
:dyn: No
:vartype: Boolean
:default: ON
:range: ON/OFF